login
Number of n X n 0..1 arrays with no element equal to more than two of its horizontal, vertical and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.
0

%I #6 Apr 21 2020 12:59:32

%S 0,1,56,2146,41931,547197,5219491,39260363,247768745,1379016025,

%T 7040775017

%N Number of n X n 0..1 arrays with no element equal to more than two of its horizontal, vertical and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.

%C Diagonal of A280810.

%e Some solutions for n=4

%e ..0..1..0..1. .0..0..1..0. .0..0..1..0. .0..1..1..0. .0..1..0..1

%e ..0..1..1..1. .0..1..1..1. .1..1..0..1. .1..0..0..0. .0..0..0..1

%e ..0..1..0..0. .0..0..0..1. .0..0..1..0. .0..1..0..1. .1..1..1..0

%e ..0..0..1..1. .1..1..0..1. .1..1..1..0. .0..1..1..0. .0..0..0..0

%Y Cf. A280810.

%K nonn

%O 1,3

%A _R. H. Hardin_, Jan 08 2017